1970s Zenith Console - Troubleshooting

[BeamT]

Originally Posted by ThePlague

Is there a more suitable way to lengthen high voltage cables besides finding the right kit?

IMO Probably not without a suitable insulated inline connector. Zenith in later designs evolved away from the exposed focus tie point on the flyback frame. The "CAUTION HIGH VOLTAGE AREA" label to the left of the tie point is quite appropriate.

It looks like the ECG or NTE HiDIV4 which is also a SK3871/DIV-4 is a nice part to have for this application. Multiple mounting options and long leads for every need.

Not to confuse things but you still have the option of going to a Tripler with an internal divider. I will try to post a scan from Sams 1375 tomorrow that indicates the Late Production 25DC56 and 25DC58Z went to a 212-141 Tripler. Which was "Preferred to CR224 and R361"

If you plan on watching this set, which is a really nice TV, the best advice would be to use the right part in the end, whichever direction you go with the focus divider. What you have now was useful for troubleshooting. Interesting, the Avanti series are still sought after. One of the few sets you could sell and get your money back out of it...... you would not want to quit your day job...

In your previous pictures the greenish tint on the back of the CRT socket is an ominous sign.

Don't forget the Degaussing thermistor from your earlier post. I can't tell from the picture if it is cracked or the lead broke off or not.

[BeamT]

These are the changes documented in Sams for the 25DC56 Late Production. I haven't had any luck finding a copy of the Zenith manual. Interesting they added the spark gap as well.

[Findm-Keepm]

Originally Posted by ThePlague

Is there a more suitable way to lengthen high voltage cables besides finding the right kit?

Easy Peasy. Double wall heat shrink and corona dope - Corona Dope is an anti-corona coating with a high voltage/mil strength that is used to prevent arcing. Double wall heat shrink (available from NTE) is what we used - with 100% success.

Corona Dope - GC 10-5002 is the good stuff. Dod specified it for connections above 40KV on airborne radars, followed by Humidseal. We used it with the AWG-9 (Tomcat) radar. Let it dry well before shrinking the heat shrink to prevent cracking (from uncured layers within...)

Double-wall heatshrink - NTE Part No: 47-23248-R (red) - 3;1 shrink ration, 3/16" and 1/4" cover 90% of electronics needs for HV insulation.

Our bench test jig HV connection was jury-rigged - we used a plastic squeeze bottle like they use for ketchup in restaurants. It kept the connection from arcing - and only one hole needed drilling.

[ThePlague]

Originally Posted by BeamT

IMO Probably not without a suitable insulated inline connector. Zenith in later designs evolved away from the exposed focus tie point on the flyback frame. The "CAUTION HIGH VOLTAGE AREA" label to the left of the tie point is quite appropriate.

It looks like the ECG or NTE HiDIV4 which is also a SK3871/DIV-4 is a nice part to have for this application. Multiple mounting options and long leads for every need.

Not to confuse things but you still have the option of going to a Tripler with an internal divider. I will try to post a scan from Sams 1375 tomorrow that indicates the Late Production 25DC56 and 25DC58Z went to a 212-141 Tripler. Which was "Preferred to CR224 and R361"

If you plan on watching this set, which is a really nice TV, the best advice would be to use the right part in the end, whichever direction you go with the focus divider. What you have now was useful for troubleshooting. Interesting, the Avanti series are still sought after. One of the few sets you could sell and get your money back out of it...... you would not want to quit your day job...

In your previous pictures the greenish tint on the back of the CRT socket is an ominous sign.

Don't forget the Degaussing thermistor from your earlier post. I can't tell from the picture if it is cracked or the lead broke off or not.

Thank you for the info on the substitution! My apologies in the delay, I had to step away from the set for a couple weeks. This TV will be a daily driver once I get it all sorted.

I've got a saved search should a 212-141 show its face, but so far no luck. Unless the focus divider I am using just doesn't work out, it will probably stay as I also have a NOS 212-130 universal tripler ready for use.

I agree on the socket, that will be taken apart and cleaned. Hopefully it doesn't require a replacement. I have also ordered a replacement thermistor per the service manual (surprisingly still available). The old one is cracked in half. Apparently it is common for these to just crumble away over the years.

[ThePlague]

Originally Posted by Findm-Keepm

Easy Peasy. Double wall heat shrink and corona dope - Corona Dope is an anti-corona coating with a high voltage/mil strength that is used to prevent arcing. Double wall heat shrink (available from NTE) is what we used - with 100% success.

Corona Dope - GC 10-5002 is the good stuff. Dod specified it for connections above 40KV on airborne radars, followed by Humidseal. We used it with the AWG-9 (Tomcat) radar. Let it dry well before shrinking the heat shrink to prevent cracking (from uncured layers within...)

Double-wall heatshrink - NTE Part No: 47-23248-R (red) - 3;1 shrink ration, 3/16" and 1/4" cover 90% of electronics needs for HV insulation.

Our bench test jig HV connection was jury-rigged - we used a plastic squeeze bottle like they use for ketchup in restaurants. It kept the connection from arcing - and only one hole needed drilling.

The parts you listed have just arrived in the mail. I've never seen so many warnings of death and harm on a such a small bottle...

I'll be waiting for a warm day to do this outside. Thank you for the recommendations!

[ThePlague]

Finally had a nice warm day. I was able to correctly extend the divider wires with the red-x corona and double wall shrink tubing. So far no arching!

I opened up the picture tube socket and it was pretty clean. I removed any light dirt/traces and buttoned it back up. The degaussing circuit thermistor was replaced with an equivalent IAW the service manual. I also replaced the divider resistor with the one including in the kit (I forget the ohms off the top of my head). It helped with the focus, but what you see in the pictures is maxed out. For good luck, I cleaned all of the dura-module pins and re-seated each one.

Long story short, we have some real life now! I gave it a quick pass with the deguass wand and that sorted out most of the impurities. However, it is in dire need of a convergence alignment. I'm hoping that this will help with focus as I am still not impressed with it. The picture is currently wider than it out to be (need to find the horizontal adjustment) and there is some vertical linearity issues that the adjustment couldn't quite sort out.

Next up is to de-oxit the control pots and work on going through the service manual for calibration.

Is there anything that I should replace on the dura-modules before continuing? This TV will be a daily driver once fully up and running. Of note, I got a nasty shock when I touched the metal frame around the picture tube on the front of the TV after powering it up for the first time. It did not occur again. Not quite sure what was the cause of that.

[zeno]

On the 9-57 hoz board check for a 330 ohm IIRC. go to a
1 watt film.
Clean the service switch ( rear ) & normal - align sw ( top ).
Semis on modules if they plug in should be cleaned. If they go int
remove the socket. The sockets were more trouble than the parts.
Remember when doing the conv. the center is ONLY the center.
Ignore T, B, & sides. Brite & contrast should be about 1/2 turn
so as not to drive it too hard.

73
Zeno

[Electronic M]

If the set is focusing such that you can defocus by rotating the control either direction from optimum, turn down the brightness some and adjust the focus again as well as the fine tuning...If the pot is at one extreme adding something 2M resistance to the end the end it's butting up against may help.

[ThePlague]

Hello all,

Sorry for the hiatus again. I've had time to spend a solid day working on this set. Items replaced before starting:

S-84384 coil (my slug broke inside)
212-72 rectifier (mine was cracked and falling apart)

I was able to replace all but the Chroma Duramodule with NOS modules that I happened upon.
I added another 2M ohm to the focus pot such that I can get to either side of out of focus and then center it. Personally I think its still blurry but that is either my expectations are a little high for the set.
I also noticed that the image is shifted to the right. I cannot find any horizontal position adjustments however.

Following the manual and advice I just cannot seem to get this set to align properly. My left and right sides are always out of alignment against the blue no matter what is tried. Convergence strips needed maybe? Below is the best I could get after about 4 hours. Given the age of the set, what level of compromise should I expect?

[old_tv_nut]

Is the vertical linearity as bad as it looks in the photo, or is it just the angle of your camera? Bad vertical linearity can affect convergence.

[ThePlague]

Originally Posted by old_tv_nut

Is the vertical linearity as bad as it looks in the photo, or is it just the angle of your camera? Bad vertical linearity can affect convergence.

The angle of the photo skews it. Its not perfect, but its not to that degree. I am going to try adjusting the purity tomorrow and see if that helps any moving forward.

[zeno]

The pix is not up to how they looked. I think the CRT is a little weak.
That will make it hard to set up. Cant tell for sure from up here in NH. !

Check a few things.
Boost, 1K resistor on focus pin if CRT, be sure instant on
is working. Also for laffs check the CRT date codes & EIA ## to
see if its OEM. Check diodes on convergence panel.

73 Zeno
LFOD !

[old_tv_nut]

In the earlier picture with crosshatch and circles, the height is way too big. If this is still true, it will affect convergence. Make sure the height is correct before proceeding.

[ThePlague]

Originally Posted by zeno

The pix is not up to how they looked. I think the CRT is a little weak.
That will make it hard to set up. Cant tell for sure from up here in NH. !

Check a few things.
Boost, 1K resistor on focus pin if CRT, be sure instant on
is working. Also for laffs check the CRT date codes & EIA ## to
see if its OEM. Check diodes on convergence panel.

73 Zeno
LFOD !

Too bad I didn't get this far on it while I was still in CT last year!
I am not sure what you mean by "Boost" but I checked the resistors out when I had the socket apart, all good there. Instant on is working.

I attempted to re-do my purity and I think that helped a bit. I re-seated all of the Semis. The 221-46 Semi on the Chroma Duramodule had two legs fall apart. Thankfully I had a NOS one from another Duramodule and that did the trick.

The CRT is OEM and an AG125VB0P22 (if I read the faded label right) with a date code of 4-13 punched out. Early on I complained of faint letterbox burn in. It never came across in the pictures, but it is certainly there. It wouldn't surprise me that this is a high mileage set. The red gun certainly seems weaker/more orange in comparison to blue and green when turning each color down.

Below are my best shots so far. I'm going to order some convergence strips for the left side. But other than that this may be where the set sits for awhile as I am bit burnt on it.

Is it feasible to source an Chromacolor tube for this unit? I have heard of people who hoard them.

[ThePlague]

I'm 95% I am dealing with a weak CRT. Hopefully I can find someone with a tester near Denver area.

Would replacing the HV tripler help at all? If that HV divider was destroyed its a possibility the tripler took some damage. I am not sure what the symptoms of too low of HV would be though.